Monday, June 15, 2015

This is a simple stereo FM radio receiver circuit that can scan with 87.5 MHz and 108 MHz seamlessly between 100 kHz step and it use BK1080 as a receiver IC.

Main components of this receiver are a PIC16F88 micro-controller, 16x2 LCD and BK1080 FM receiver chip. This system is design to work with 5V DC power supply. User interface of this system consist with 6 push buttons and a 16×2 character LCD module. All the functions of this receiver can control by this buttons and necessary information displayed on the LCD.

Specifications of this receiver

Easy to build

Standby mode

Automatic gain control

Automatic frequency control

Automatic noise suppression

Preset memory stations up to 250 (default 20)

Schematic of BK1080

BK1080

The BK1080 FM receiver employs a low-IF architecture, mixed signal image rejection and all digital demodulation technology. The stations scan of BK1080 searches radio stations based on both the channel RSSI estimation and signal quality assessment, increases the number of receivable stations while avoids false stops. BK1080 enables FM radio reception with low power, small board space and minimum number of external components. All functions controlled through an I2C serial interface. See datasheet for more details.

Numbers of memory locations are determine by the value of Eeprom 1 (default value 0x14).
You can connect an earphone directly with BK1080’s output. However, do not connect speakers directly with IC. I recommended you to use amplifier if you wish to get more sound. In addition, be carefully when soldering BK1080. Because this IC more sensitive to electrostatic. Use DC soldering Iron to solder this IC or unplug your iron when solder. Micro-controller runs using its internal oscillator. RA0 and RA1 are configuring as SCL and SDA. RA2 is not connected. RA6 pin can directly connect with background light of LCD display. As well as it is also can used for the controlling another device like mute pin of power amp.

Selecting the station:
When we are in the power on mode, on the screen we can see "Frq:107.5 Ch:12" - tuned frequency of the station and then the number of the cell where the recorded frequency of the station. Pressing ‘CH_UP’ and ‘CH_DN’ we can move the recorded stations. Pressing ‘FR_UP’ and ‘FR_DN’ we can change the frequency. ‘STORE’ stored the current frequency to the current station and ‘PWR’ used to toggle standby mode and power on mode

Firmware of this system was written by using MikroC for PIC and schematic, hex and Proteus files are available for download.

Saturday, June 13, 2015

This is high quality stereo digital PLL synthesized FM radio receiver circuit that can scan with 76 MHz and 108 MHz seamlessly between 100 kHz step, although the sensitivity is high.

Main components of this receiver are a PIC16F88 micro-controller, 16x2 LCD, LM7001 PLL Frequency Synthesizer, AN7223 IF Amp, TA7343 MPX and a FM Tuner. This system is design to work with 12V DC power supply and the LM7805 and 7808 regulators used to manage power requirements to the above-mentioned components.

User interface of this system consist with 6 push buttons and a 16×2 character LCD module. All the functions of this receiver can control by this buttons and necessary information displayed on the LCD.

Specifications of this receiver

High sensitivity

Standby mode

Preset memory stations up to 250 (default 20)

3-user selectable frequency ranges (default 87.5-108)

Schematic of PLL and Power circuit

Schematic of micro-controller and user interrface

LM7001

The LM7001 is a PLL frequency synthesizer LSIs for tuners, making it possible to make up high performance AM/FM tuners easily. These LSIs are software compatible with the LM7000, but do not include an IF calculation circuit. The FM VCO circuit includes a high-speed programmable divider that can divide directly seven reference frequencies. Serial input circuit for data input (using the CE, CL, and DATA pins)

Tuner

Anticipating the objection that these tuners do not find, I assure you that if you do not be lazy and go through the repair shops where repair radio. In addition, you can get this tuner from old audio system and car set. There are 3 types.

Types of tuner

FM Front End only (you need to build IF Amp, MPX circuit)

FM Front End with IF (you need to build MPX)

FM Front End IF and MPX

IF Amp and MPX

For IF amp I used AN7223 because it need few external parts and it has high sensitivity and stability. If you cannot find FM quad coil then you can use 2pin 10.7MHZ ceramic resonator for that (see datasheet for more details). However, it is possible to use another IC for this as AN7220, TA7640 and KA2297 etc.

For MPX decoder here I used TA7343. This IC decode mono signal to stereo. This is an optional part. If you wish to work with mono, then omit this part and connect amplifier input with ‘AF’.

IF and MPX circuit

Complete circuit

Operation

Numbers of memory locations are determine by the value of Eeprom 1 (default value 0x14) and frequency range is determine by the value of Eeprom 2 (default value 0x00).

If value is 1 then range is 76-108MHz

If value is 2 then range is 76-90MHz

Else, range is 87.5-108 MHz

Selecting the station:
When we are in the power on mode, on the screen we can see "Frq:106.5 Ch:15" - tuned frequency of the station and then the number of the cell where the recorded frequency of the station. Pressing ‘CH_UP’ and ‘CH_DN’ we can move the recorded stations. Pressing ‘FR_UP’ and ‘FR_DN’ we can change the frequency. ‘STORE’ stored the current frequency to the current station and ‘PWR’ used to toggle standby mode and power on mode

Micro-controller runs using its internal oscillator. RA6 pin can directly connect with background light of LCD display. As well as it is also can used for the controlling another device like mute pin of power amp. For VCC (tuning voltage) you can use up-to 12v.

Firmware of this system was written by using MikroC for PIC and schematic, hex and Proteus files are available for download.